The present invention relates to a spring apparatus and a product employing the spring apparatus and, more particularly, to a spring apparatus having an extremely long extensible and contractible stroke and being capable of obtaining substantially constant repulsion force over the entire stroke, and also to a product utilizing the characteristics of the spring apparatus.
A compression coiled spring has heretofore been frequently used. Its extensible stroke is relatively short, and variations in its repulsion force are large over the entire stroke. This drawback become prominent when the spring is used as a spring apparatus in a special product.
For example, in an apparatus for lifting a heavy load, it is preferable to support the heavy load by the repulsion force of the compression coiled spring. In this case, the above-mentioned drawback results in great defects. The drawback also brings forth great disadvantages when the compression coiled spring is used as an actuator in various types of devices used in outer space. More specifically, since the stroke of the spring is short, the entire spring must be large and heavy to obtain a necessary stroke. Since the variations in the repulsion force of the spring is large in the entire stroke, structural members and a latch mechanism for holding the spring in a compressed state must be designed to endure the maximum repulsion force of the spring, and must therefore be large and heavy.
Heretofore, to eliminate or diminish the above-mentioned drawback of the spring, various types of techniques have been developed. These techniques reside in improving the properties of materials of the spring, for example, by increasing the elastic limit of the spring and by using light materials. However, the improvement of the material properties is insufficient.